Frequently Asked Questions
JUXTA Series Signal Conditioners
Specifications
Questions
Instrument selection
Input specifications
Output specifications
Operating specifications
Computing units
Answers
Instrument selection
| 1. Please explain the advantages of the plug-in conditioner. |
| Since it can be separated from a socket, you can do panel work even without a conditioner. Maintenance is easy because it can be exchanged simply by plugging or unplugging the main unit. Another advantage is that you don't have to perform any wiring. |
| 2. Please explain the advantages of the front panel terminal type conditioner |
| Possible to mount in a rack, on a DIN rail, or on a wall. Signals can be checked when instruments are running, or with live wires (assuming the operator has experience checking signals). |
| 3. Please explain the advantages of the nest-housed conditioners |
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Generally these can be used for DCS connections. The following are the advantages: -16 units can be housed per nest. -Checks can be made actively. -Card configuration allows easy insertion/removal. -One source can power all units together. |
Input specifications
| 1. With pulse input, there is an "internal load resistance," but what does that mean? |
| This is specified for current pulse input. Resistance values specified depends on the specification of the transmitter (mainly the rated current of the open collector). The internal load resistance are 200 ohm, 500 ohm, and 1 kohm, and power supply supplied from the transmitter is 0.5 W or 2 W depending on its specifications. (The VJP8 is attached externally. 200 ohm (0.5 W) of the external resistance is available.) |
| 2. I don't understand how to determine the internal load resistance. |
| For example, if the specifications of the open collector on the output side indicate 30 V/30 mA, use an internal load resistance of 1 kohm (transmitter power supply 24 V). This results in a 0/24 mA current pulse. |
| 3. What is the input resistance during current input? |
| It is 250 ohm (4-20 mADC). However, certain computing units also have 100 ohm input. |
| 4. The Pt100 ohm standard refers to IPTS-68, ITS-90, and JPt100 ohm. What is the difference between these? |
| IPTS-68: An international standard from 1968 in which R100/R0=1.2850. JIS adopted the standard between 1989-1997, but it is not presently used. ITS90: An international standard from 1990 in which R100/R0=1.3851. JIS has adopted the standard from 1997 to the present. JPt100 is a Japanese standard that was cancelled in 1989, in which R100/R0=1.3916. |
Output specifications
| 1. What is the allowable load resistance? |
| This is the input impedance of an instrument that can be connected to the output terminals, or the receiving resistance when the conditioner is outputting current. The wiring resistance must be added and taken into account. |
| 2. How many instruments can be connected to the current output terminals (4-20 mADC)? |
| For most current input type instruments, the input impedance is 250 ohm. The corresponding allowable load impedance for current output is 750 ohm, therefore the max. number of connectable units is 3. |
| 3. How many instruments can be connected to the voltage output terminals (1-5 VDC)? |
| For most voltage input type instruments, the input impedance is 1 Mohm. The corresponding allowable load impedance for voltage output is 2 kohm, therefore the max. number of connectable units is 500. |
| 4. I'm working with an open collector, and I have the conditioner output connected to a counter or relay but it doesn't work. |
| Because it is an open collector, you need to add a power supply. Be sure to pay attention to the maximum allowable load when doing so. |
| 5. What would the frequency setting be for an analog pulse converter if I want to output an integral pulse from a 100 m3/H flowmeter as 10L/P? |
| It would be: 100×1000/10/H = 10000/3600 Hz = 2.778 Hz (The number of significant figures is 4.) |
Operating specifications
| 1. What is output during burnout? |
| It is over 106% of the output range when UP, and less than -6% when DOWN. |
| 2. I see a response time of "**ms (10-90%)," but what does that mean? |
| This is the time required to reach an output of 63% with 10=<90% step input. |
| 3. The response is 63% or 90% depending on the manufacturer, but how can I compare these? |
| Multiply the response time at 63% by 2.3 to get the equivalent response time at 90%. |
| 4. What temperature/pressure computing unit should I use depending on the flow detection system (differential pressure type, vortex-type)? |
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| 5. What temperature/pressure computing unit should I use depending on the measured fluid? |
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| 6. Total resistance is used for ordering slide resistance converters. What is the total resistance value for the models with zero and span resistance specification? |
| Total resistance value >= zero side resistance + span resistance. |
| 7. How does the unit operate when burnout is OFF? |
| If input is broken it scales off to the upper or lower limit, but there is no rule as to which. |
| 8. With a PT100, I have burnout set to UP, but are there cases where it scales down, or starts at the lower limit when it recovers? |
| If either one of the wires is broken or disconnected it scales off to the upper limit. If the connection is restored when the wires are hot, it may immediately scale down due to the wiring contact, but once the connection is secure it will perform stably according to the response time of the converter. |
| 9. Please explain the meaning of "time constant." |
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In the case of a conditioner, the time constant indicates the response time. Expressing this as a transfer function: it is expressed as: OUT = IN * (1-eEXP(-t/T)) where OUT = output, IN = input, e = natural log, T = time constant, and t = time elapsed. If the elapsed time is equal to the time constant, the e index is -1, and OUT becomes 63% of the value when IN changed. If even more time passes, the index item approaches -infinity, and OUT equals IN. |
Computing units
| 1. What is a conditioner that can compensate temperature and pressure from a differential pressure flowmeter (ideal gas)? |
| The MXT-R. |
| 2. What is a conditioner that can compensate temperature and pressure from a vortex type flowmeter (ideal gas)? |
| The MXT-T. |
| 3. What is a model that can compensate temperature and pressure of steam? |
| Please use the MXT-A free programmable model. |
| 4. What is a model that can perform Astem compensation? |
| It's not a comprehensive solution, but if you can specify the type of fuel oil the MTX-A free programmable model can do this. When changing the type, the compensation curve changes. |
